With the takedown of Anwar al-Alwaki, one more leadership piece of al-Qaida has been smashed. But even more importantly, this demonstrates the effectiveness of the US's adaptation to strike directly and covertly at terrorists, anywhere in the world.

In the immediate aftermath of 9/11, the United States had to strike at al-Qaida in Afghanistan. And we did so, with about 300 special forces on the ground and powerful precision-strike air support overhead. In the process, we took down the Taliban government of Afghanistan – but we missed much of al-Qaida, which escaped to Pakistan. Over the years, al-Qaida tried to pull off other big strikes, with diminishing success, and also dispersed geographically, morphing into al-Qaida in Iraq, al-Qaida in the Arabian Peninsula, and so on.

But the US didn't stand still, either. Where al-Qaida mustered and fought, they were defeated – as in Iraq. And where they have dispersed and attempted to rebuild their bases, they are being pursued, relentlessly and very efficiently, by the United States.

Instead of deploying tens of thousands of troops in dozens of countries, we have worked with allies, honed intelligence, and developed remarkable precision-targeting and strike capabilities. For the US, it has been a new way of war, fought largely out of sight by the CIA and special forces personnel. It is waged 24 hours per day, often in failed and failing states, but also in many countries the average American tourist wouldn't suspect. For the United States, which was a novice in the intelligence and special operations business in the second world war, and whose agencies were roughly treated in the aftermath of Vietnam, this has been an incredible transformation.

For Alwaki, the journey is over. His death makes his final legacy a proof of the effectiveness of America's active defense against terrorists. For the United States, the journey continues: Awlaki's death also moves us closer to the time when we must transition, psychologically and practically, from being a nation under threat to a nation that once again champions its openness and welcome to the whole world.

As with the adaptation to face al-Qaida, the transition can be done. It must be worked carefully, for there are still those who would harm America. But it is a transition that must take place, for our greatest strengths lie in living courageously our own values.